Piezoelectricity is the property of a material to

• A. absorb energy in the form of heat
• B. produce a voltage when deformed and vice versa
• C. reflect sound waves
• D. conduct electricity

Answer: (B)

Piezoelectricity is the coupling between mechanical deformation and electric potential in certain materials. When you squeeze or bend a piezoelectric crystal, charges separate and a voltage appears on its surfaces. Conversely, applying a voltage causes the crystal to deform or vibrate. This bidirectional electromechanical effect is what lets ultrasonic transducers generate sound waves and also detect echoes by converting mechanical vibrations back into electrical signals. The other ideas don’t fit this concept: absorbing energy as heat describes damping, not voltage generation; reflecting sound waves is about how sound interacts with boundaries, not the material’s internal coupling; and conducting electricity is about charge flow, not producing voltage from deformation or inducing deformation with an electric field.